When a drop with a complex composition --such as those exhaled in respiratory activities-- evaporates in an acoustic levitator, its properties change over time as the most volatile component (water) evaporates. This leads to a reduction in the drop's surface tension which, in turn, causes the drop to flatten as a result of the push of the same acoustic pressure forces that keep it levitated. And then, when the flatteing exceeds a critical value ... topological transition happens! In a matter of milliseconds, the flattened drop buckles to turn into a "soap bubble" which remains stable for several minutes. This topological transition is a rather violent process which generates two powerful Worthington jets : one that escapes downwwards, and another one that is devoured by the drop-turned-into-bubble to result into a tiny encapsulated drop. A Fluid Mechanics allegory of the mythological picture of a Titan devouring his son.
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